How much water does the body really need?

Taking a water bottle to the gym or drinking a certain amount of water each day may seem like good choices. But do they provide health benefits? This week on WRVO's health and wellness show "Take Care," hosts Lorraine Rapp and Linda Lowen speak with Dr. Stanley Goldfarb, professor of medicine at the University of Pennsylvania. Dr. Goldfarb explains what his research has shown about why water is so important to the body but how you may not need as much of it as you think.

Lorraine Rapp: Would you explain what role water plays in the body? Where does it go once we drink it and what function does it serve?

Dr. Stanley Goldfarb: Sure. Our body is composed of anywhere between 50 to 70 percent of water. So, obviously, water is crucial to health, it’s crucial to life. And because it’s so crucial to health and so crucial to life, we have multiple systems that are ingrained in our metabolism that make sure we keep that water content very constant. So then, water is crucial to body functions. And any water that’s ingested doesn’t stay in any one particular compartment, but distributes itself throughout the body and then is rapidly excreted until the amount of water in the body returns to the baseline.

Lorraine Rapp: So it sounds like you’re saying: drink when you’re thirsty, but above and beyond that it’s not necessary. What science is behind that?

Dr. Goldfarb: I think when you’re thirsty it does indicate that 1 or perhaps 2 percent of the total amount of water in the body has been depleted. And this could certainly happen when someone’s exposed to a hot environment or exercises very vigorously. But at that point if you start drinking, there are no real consequences to your health to wait until you are thirsty in order to drink. And there have been studies looking very carefully at athletic performance in individuals who pre-hydrate and never allow even the 1 percent decline in total body water that might occur during vigorous exercise. And this has been done in really elite athletes. And there’s just no evidence that there’s any impairment in their performance if they don’t pre-hydrate and hydrate during their exercise compared to those that do.

Lorraine Rapp: How much water should we be drinking on a daily basis for optimum health?

Dr. Goldfarb: Well, I think most of the studies suggest there is no amount of water that you need to drink for optimum health. Once you get above the amount that’s obligate losses through the day, which probably comes out to be somewhere around one and a half to two quarts a day, that’s probably an absolute obligation, simply because you’re going to lose that much through the skin and through the obligate losses in the urine. As long as you equal that, you’re going to stay in water balance and have absolutely no consequences to your health. So if you allow yourself to get thirsty, as soon as that thirst occurs, you’re going to start to drink and you will make up enough water to accommodate those obligate losses you have each day. The question has been whether going above those obligate losses and making sure that you drink, not only in addition to the amount you are required to by thirst and by obligate water losses, drinking above and beyond that is going to produce any health benefits, and that’s where it’s quite clear that there’s just no evidence to support that.

More of this interview can be heard on Take Care, WRVO's health and wellness show Sunday at 6:30 p.m. Support for this story comes from the Health Foundation for Western and Central New York.